I am a decorator and had 2 chairs made with a heavy linen fabric for a client 7 years ago. The fabric on the back cushions and the seat cushions have become discolored and mottled, almost like tie dye. The cushions are down backs and spring down seats. You can see a pattern of the casing material. There is no discoloration anywhere else on the chairs. It looks like some kind of chemical reaction to something, but she has not had them cleaned or applied any cleaner to the cushions. Also, they are not in direct sun light. I can send you pictures if that would be helpful. Help!!